OAKLAND -- A 20-year-old man on probation for grand theft has been arrested on suspicion of robbing five East Bay banks, including one North Oakland branch twice, police said Monday.

Police said Amanuel Moreno, of Oakland, has admitted his involvement in the robberies, telling investigators he needed money to feed his family.

Investigators say the robberies happened Jan. 16 and Dec. 6 at the Bank of the West, 4900 Telegraph Ave., in North Oakland's Temescal district; Dec. 18 at the U.S. Bank in San Leandro; Dec. 18 at the Chase Bank in Union City; and Dec. 13 at the Wells Fargo branch in Hayward.

He is also suspected of robbing a Chase Bank branch in Alameda on Dec. 6 but has not admitted his involvement in that heist, police said.

Police said in the robberies Moreno, a former security guard, gave demand notes to tellers and occasionally indicated he had a gun, although none was ever seen. In the Dec. 6 Bank of the West robbery, a dye pack was included in the cash that was taken. The dye pack later exploded. Moreno told police he had put the money in a plastic bag, preventing him from getting doused with dye when the pack exploded, authorities said. The same branch was robbed three other times in December, but no arrests have been made in those cases.

Oakland police Officer Nick Calonge said a fellow officer recognized Moreno from a Bank of the West surveillance photograph, and he was arrested Friday night at his home on 38th Street.

Authorities said Moreno was arrested for robbery in 2011 but in a plea deal was convicted of grand theft in March 2012 and placed on probation. He is being held without bail for violating probation pending filing of formal charges in the bank robberies, authorities said.