OAKLAND, CALIF., MAY 26 -- The FBI is investigating possible links between a car-bomb blast that injured two radical environmentalists accused of carrying the explosives and a recent bombing at a lumber mill, officials said today.

Earth First! activists Darryl Cherney and Judi Bari, who have been waging a campaign to slow logging in Northern California's old-growth forests, strongly denied knowing anything about the pipe bomb that injured them Thursday.

The two were put under arrest Friday after police questioned Cherney for several hours.

Bari, 40, was under police guard at a hospital where she was in stable condition after surgery for a fractured pelvis, officials said. Cherney, 33, was treated for minor injuries and booked into city jail.

Oakland Municipal Court Judge Horace Wheatley raised bail to $100,000 each, citing new information from Oakland police. He declined to elaborate.

No charges were immediately filed, but Police Lt. Mike Sims said at a news conference, "The evidence is strong they were transporting this device and that's why they were arrested."

Sims said three search warrants were used to find evidence he would not specify that led to the arrests. Police Thursday searched Cherney's van and a Berkeley house occupied by several members of another environmentalist group, Seeds of Peace. On Friday they searched Bari's home near Ukiah.

The Tribune of Oakland quoted unidentified law enforcement sources today as saying that Bari placed her guitar case over the bomb, which was located behind the driver's seat, suggesting that she knew the device was in the car.

Finishing nails identical to ones used in the bomb were found elsewhere in the car, and similar nails were found during a search of one of the suspect's home, the sources said. Duct tape and wire resembling that used in the bomb were found in Cherney's van and home and also in Bari's house, they said.

Duke Diedrich, spokesman for the FBI in San Francisco, said the bureau planned to send remnants of the pipe bomb to its headquarters for analysis and comparison to remains of a pipe bomb that exploded May 10 outside a lumber mill in Cloverdale, about 80 miles north of San Francisco. That blast caused no injuries and only minor damage.

The FBI is also investigating possible links between Friday's explosion and sabotage of Pacific Gas & Electric transmission lines in Santa Cruz County last month that left thousands of residents without power throughout the county.

"We will conduct and have been conducting an investigation throughout Northern California to see if any of the incidents are connected in any way," Diedrich said. "This is going to be a long, involved investigation."