OAKLAND — Police have arrested four men suspected in two recent robbery sprees at the Montgomery and Richmond BART stations, and they are seeking help to find more suspects and victims, transit district officials said Wednesday.

Oakland resident Donail James, 23, was arrested Sunday at the Montgomery station in San Francisco. Prosecutors have charged him four counts of robbery and one count of possession of stolen property, crimes that authorities say he committed at that station.

“This man was so bold and brazen during the at least four robberies we know of, he simply thought he could just walk through the middle of the Montgomery Street BART station and possibly get away with another one,” BART police Lt. Andy Alkire said.

Investigators think that James was involved in more robberies. Police said anyone with information on possible robberies should call 877-679-7000, ext. 7040.

In the second case, three men surrounded a customer at the Richmond BART station Monday, demanded his money and threatened to beat him if he refused, according to BART police.

The victim was able to break away and report the incident to a station agent, who called BART police.

When officers responded, the suspects remained at the station and were arrested, police said. The suspects are Landon Sims, 23, of San Pablo; Antonio Thomas, 20, of Richmond; and Clifton Hall, 28, of Richmond. All three remained jailed Wednesday at County Jail in Martinez. They are facing attempted robbery charges.

BART police said that despite the recent robberies, overall violent crime in the transit system is down 26 percent and robberies are down 30 percent compared with this time last year. Overall crime on BART is down 7.6 percent.

Contact Sean Maher at 510-208-6430.