OAKLAND — A Livermore man on probation for a federal narcotics conviction was arrested Thursday evening after the Alameda County Narcotics Task Force seized 11½ kilos of powder cocaine with a street value of more than $2 million.

Alameda County Deputy Sheriff Steve Angeja, a task force supervisor, said Friday that the suspect, Javier Martinez, 36, whose street name is "Cheeks," supplied the drugs to dealers across Oakland, where he grew up.

Also arrested was Martinez's girlfriend, Valentina Lopez, 35, who authorities said is eight months pregnant with his child.

Authorities also found $15,000 worth of crystal methamphetamine, $3,400 worth of rock cocaine and about $100 worth of Ecstacy pills at the so-called "stash pad" in the 24500 block of Mohr Drive in Hayward, Angeja said.

The arrests and seizures ended a two-month task force investigation headed by Oakland Housing Authority Detective Ramon Jacobo, who received information that Martinez was selling kilos of cocaine at a time to Oakland drug dealers.

Angeja said the task force put Martinez under surveillance for "hundreds of hours," learning where the stash pad was and watching him make deliveries.

A search warrant was served at the Mohr Drive apartment about 5:30 p.m. Thursday. Martinez was arrested as he was bringing a duffel bag containing eight kilos of cocaine from the apartment to a rental car where Lopez was waiting, Angeja said. Another 3½ kilos

Martinez's home on Glenn Common in Livermore was searched, but nothing was found there.

Authorities said Martinez was released from federal prison on probation in February after serving eight years for a 2001 conviction involving 16 kilograms of cocaine. He also served three years in state prison for a 1997 Oakland case in which then-Officer Sharon Williams, now a lieutenant, arrested him for possessing two kilos of cocaine.

Martinez and Lopez were arrested on suspicion of possession of cocaine for sale and possession of methamphetamine for sale. They are each being held on $500,000 bail. The investigation is continuing, and more arrests could be made, Angeja said.

Thursday's seizure by the task force was its biggest in recent months involving suspected Oakland drug dealers.

On June 10, Timothy Crawford, 47, a suspected major dealer in the Seminary Avenue area, was arrested in the 2900 block of 60th Avenue, where the task force found a kilo of cocaine worth $200,000, a pistol and $43,000 in cash, Angeja said. That investigation was headed by sheriff's Deputy Johnnie Graham and included an undercover officer buying cocaine from Crawford, Angeja said.