Marking 25 years since the deadliest domestic terrorist attack on U.S. soil, federal authorities on Thursday warned law enforcement agencies across the country that the threat from violent white supremacists and anti-government extremists remains “persistent and evolving.”

“The prevalence of lethal [domestic terrorist] attacks in the 25 years following the bombing of the Alfred P. Murrah Federal Building in Oklahoma City highlights the continued threat they pose,” the FBI, Department of Homeland Security and National Counterterrorism said in a joint intelligence bulletin issued nationwide.

The bulletin noted that the April 19, 1995, bombing by anti-government extremist Timothy McVeigh killed 168 people and injured several hundreds more, making 1995 the nation’s deadliest year for domestic terrorist attacks.

The nation’s second-most lethal year for such attacks was last year, when domestic terrorists killed at least 31 people, 23 of which were killed by white supremacists, according to the bulletin.

"While threats from [domestic terrorists] have continued to evolve since the Oklahoma City bombing, many of their significant drivers have remained constant,” the bulletin added, pointing to “perceptions” of government “overreach,” reactions to immigration policies, and the advocacy for “the superiority of the white race."

The bulletin mentioned several recent cases, including February’s attempted arrest of suspected white supremacist Timothy Wilson in Missouri for plotting to bomb a health care facility in the midst of the coronavirus crisis.

Wilson was fatally shot when FBI agents tried to arrest him, but in the days before he “cited the likely increased impact and media attention on the health sector during the coronavirus pandemic as a reason to accelerate the timing and selection of a healthcare facility," Thursday’s bulletin said.

The bulletin also discussed the February arrest of five members of the neo-Nazi group Atomwaffen Division, whose founder allegedly kept a framed picture of Timothy McVeigh on his nightstand. It also discussed the 2017 arrest of Jerry Drake Varnell, who was arrested for trying to "seemingly replicate" the 1995 attack by bombing a bank in downtown Oklahoma, according to the FBI and Justice Department.

Varnell, who had expressed anti-government views, was convicted of federal changes that he attempted to use a weapon of mass destruction, and last month was sentenced to 25 years behind bars.

In Thursday's bulletin, federal authorities made clear that they "have no information indicating there is current attack plotting related to the Oklahoma City bombing anniversary."

However authorities urged law enforcement officials around the country to remain vigilant, providing them with a list of possible "indicators" that could mean someone is moving toward violence.