President Biden signed into law on Friday a new government program to compensate C.I.A. officers, State Department diplomats and other federal officials who have suffered traumatic neurological injuries that the intelligence community has yet to figure out, launched by assailants it cannot yet identify.

With no ceremony and little public comment, Mr. Biden signed the Havana Act, authorizing Secretary of State Antony J. Blinken and the C.I.A. director, William J. Burns, to give financial support to employees who have suffered brain injuries. The act is named for what has become known as “Havana Syndrome,” a series of unexplained injuries whose victims were first identified five years ago at the United States embassy in Cuba.

But Mr. Biden’s silence about the new law — he issued a statement, but avoided a public ceremony where he might be asked questions — was telling. While some officials are convinced the syndrome is the result of attacks and that one or more rival powers are responsible, intelligence agencies have yet to come to any firm conclusions, despite the appointment of multiple task forces to identify the cause and possible countermeasures.

There is a widespread belief, supported by a study by the National Academies of Sciences, Engineering, and Medicine, that the cause is directed energy, possibly microwaves, presumably targeted at embassies and residences. But even that is just the leading theory, and though Russia is the lead suspect, it is hardly the only country with the technology to conduct such attacks. The C.I.A. and the National Security Council have created an outside panel with access to classified information to help search for a cause.

“We are bringing to bear the full resources of the U.S. government to make available first-class medical care to those affected and to get to the bottom of these incidents, including to determine the cause and who is responsible,” Mr. Biden said of the law. “Civil servants, intelligence officers, diplomats, and military personnel all around the world have been affected by anomalous health incidents,” Biden said, stopping short of using the word “attacks.”

Jen Psaki, the White House press secretary, did not go into specifics on Friday when asked whether the episodes posed a threat to the American public, or specifically to Americans traveling abroad.

“We take every reported incident seriously and what we want to do is ensure that our national security team is using every resource at our disposal,” Ms. Psaki said. “Without an attribution and an assessment of the cause for the origin, I do not want to go further.”

The president’s signature came just as the episodes appear to be increasing in frequency and some have become more brazen: A C.I.A. officer traveling with Mr. Burns to India several weeks ago became the latest victim, in an incident that resonated inside the White House because his travels had not been publicized, and because targeting a member of the traveling party of the C.I.A. director — if that is what happened — seemed especially provocative.

The India incident came after two dozen or more cases were reported in Vienna, which is home to three U.S. embassies (two of which are linked to United Nations agencies), as well as the negotiations over Iran’s nuclear program. It is also the operating territory of spies from around the world. And over the summer, Vice President Kamala Harris’s trip to Vietnam was delayed for several hours because of concerns over incidents there.

The incidents have led to a rare example of bipartisan agreement in fiercely partisan Washington. The original bill was written by Senator Susan Collins, Republican of Maine. Representative Adam Schiff, Democrat of California, guided the bill through the House, where it passed unanimously.

Ms. Collins said she was increasingly convinced that some adversary was behind the incidents. “As we continue our efforts to support victims, we must also redouble our whole-of-government approach to identify and stop the heartless adversary who is harming U.S. personnel,” she said in a statement on Friday.

Mark S. Zaid, a lawyer who represents multiple victims, said the legislation was “a good and necessary first step but it’s woefully deficient in many ways.”

The bill leaves it up to the leaders of the C.I.A. and State Department to make their own determinations as to who is covered and how much compensation they receive, meaning “it has the opportunity to create incredible inconsistencies between agencies as to how they’re dealing with it,” Mr. Zaid said. “This is the type of case that demands uniform standards throughout the federal government. Someone at State should not be treated differently than someone at C.I.A.”

An administration official, speaking on condition of anonymity to disclose internal communications, said that officials had been trying since Mr. Biden took office to standardize what they conceded was an ad hoc and uneven reporting process among agencies, and that the State Department released guidance over the summer that assured employees they would receive the same standard of care as people from other agencies, including the C.I.A.

Victims’ groups that have been pushing for their injuries to be recognized and compensated applauded the signing. Robyn Garfield, a Commerce Department official who was injured in China, said the critical next step was to make sure victims who could no longer work were receiving proper care.

Mr. Garfield also said uniform diagnostic and treatment plans had to be adopted.

“For too long, too many of us have been treated as adversaries and not partners by our own agencies,” Mr. Garfield said.

Mark Lenzi, a State Department official who was also injured in China, said it was time for Congress to hold hearings, adding that there was more information collected by the government that lawmakers must review.

“This Havana Act legislation is crucial but only a first step towards getting injured U.S. government personnel and their family members the help we should have received years ago,” Mr. Lenzi said.

Ana Swanson contributed reporting.