Police yesterday acted on several leads to tighten their not around two Coop bandits still at large while the Cambridge District Court slapped $50,000 bail on a newly-arrested suspect.

The prisoner, booked as Jacob "Jack" Lewis, was captured last Friday in a raid on a South End hotel. Held for questioning over the weekend, he was arraigned yesterday morning and pleaded not guilty to charges of participation in January's smoke-bomb holdup.

Nick Mavrides, Cambridge nightclub operator, had been arrested previously and is still being held for $120,000 bail.

Police Expect Fast Results

As a result of Lewis' arrest, police expect to round up the rest of the gang shortly and to recover most of the missing money. $15,000 of it has already turned up in safe deposit boxes at Newton and Boston banks.

Lewis, who has a record of 30 convictions, was released from State Prison in 1941, where he had served a term for carrying a concealed weapon and possessing burglars tools. Detectives closed in on him Friday after hearing that he had just returned from a hurried out-of-town trip.

The case is expected to arrive before a grand jury within a month.