OAKLAND, MAY 24 -- A bomb explosion in a car here injured two members of a militant environmental group riding in the vehicle today, officials and witnesses said.

One of the two members of the group Earth First! said recently she had received death threats for helping organize a campaign to halt logging in Northern California's old-growth forests and for other environmental activities.

The explosion occurred shortly before noon near Oakland High School, said a garage worker who identified himself as Charles.

"It sounded like a cherry bomb in a tin can," said the worker. "It was pretty loud. I kind of felt it in my body and I was inside."

After the explosion, the car rolled about 50 yards before hitting another vehicle and coming to a stop, witnesses said. Pieces of seats and windshield covered the street.

Authorities declined to identify the victims, but Earth First! spokesman Daniel Barron said they were group members Judi Bari, 40, a passenger in the white Subaru station wagon registered in her name, and driver Darryl Cherney, 30, both of Ukiah.

Bari suffered facial injuries and a pelvic fracture and was in serious but stable condition at Highland Hospital, hospital spokesman David Berry said. Cherney was treated for a minor injury above his left eye, Berry said.

Police are certain the explosion was caused by a bomb, said a homicide investigator who spoke on condition of anonymity.

Bari and Cherney were organizers of the upcoming "Redwood Summer" campaign to stop what some environmentalists say is excessive logging in California, Earth First! spokeswoman Kelpie Wilson said. The campaign is based on the nonviolent civil rights movement of the 1960s, Wilson said.

In an interview published Sunday in the San Jose Mercury News, Bari said she has received several death threats in recent months. Other Earth First! members involved in anti-logging activities were attacked by loggers during demonstrations in Ukiah last year.