SAN DIEGO -- Several court cases will be delayed Monday after a non-injury explosion at the federal courthouse in downtown San Diego over the weekend prompted authorities to temporarily close the facility.

The blast at the Edward J. Schwartz Federal Courthouse at 940 Front St. occurred at about 1:40 a.m. Sunday and may have been caused by a pipe bomb, said FBI spokeswoman April Langwell.

In addition to the local closure, a warning was in effect Monday for all FBI offices and federal courthouses in the country.

Along with local authorities, the FBI Joint Terrorism Task Force was investigating the explosion, which damaged the entrance and lobby to the courthouse.

Some shrapnel also damaged the AT&T building that faces the courthouse, as well as an ATM machine located across the street, reported 10News.

The San Diego Union-Tribune reported that a piece of shrapnel was found lodged in the eighth floor of the AT&T building.

Evidence collected from the scene will be sent to an FBI laboratory in Virginia, where it will be analyzed by bomb experts, the newspaper reported.

As of early Monday, no one had claimed responsibility for the explosion.

"It's too early to tell if it's terrorism-related," FBI spokesman Darrell Foxworth told the Los Angeles Times. "It does not appear to be right now."

Foxworth said the explosion did not appear to be linked to any legal cases at the courthouse, either.

Officials said they don't know if the bombing is connected to a pipe bomb that exploded at a Federal Express building in San Diego last month. In that non-injury incident, a bomb shattered a glass door at the building on 47th Avenue near Federal Boulevard at about 2 a.m. on April 25.