EMERYVILLE -- A biotechnology building evacuated early in the day was given the all-clear Wednesday afternoon after a bomb threat prompted a six-hour search. Police re-opened the EmeryStation East Building at 5885 Hollis Street, as well as streets surrounding the building, at about 1 p.m., after a bomb threat brought emergency crews from four agencies to the building. Trains were halted on nearby tracks, and streets in a two-block perimeter around the area were closed to traffic and pedestrians.

No details were released about the nature of the bomb threat but the threat was specific enough to be taken seriously, said UC Berkeley police Lt. Eric Tejada.

A bomb disposal technician in protective gear entered the emptied building, which houses about 1,000 people, just before 10:30 a.m., but officials said no device was found.

Eight dogs and four law enforcement agencies searched the building, he said.

"It is not a fast process," Tejada said of the six-hour search. "The building is very large, and the dogs needed to rest at points."

The threat, reported about 7 a.m., apparently targeted the Joint BioEnergy Institute, a laboratory facility run by Lawrence Berkeley Lab in partnership with several other national laboratories. The institute works to develop fuels that can be extracted from nonfood plants.

The building takes up almost a city block, surrounded by Hollis, Powell, Peladeau and 59th streets. Completed in 2007, the building also houses facilities run by several private biotechnology firms, according to a website created by Wareham Development, the building's owner.

UC police brought in bomb-sniffing dogs and explosives technicians to help clear the building. The U.S. Department of Homeland Security and the Alameda County Fire Department also assisted.

Tejada said the investigation into the bomb threat is ongoing, and as of Wednesday night, there were no suspects in the case.

Staff writer Katie Nelson contributed to this report.