NEWPORT, R.I. (AP) _ A prisoner in a police station jail cell stabbed four officers with a makeshift knife while being held on motor vehicle charges, authorities said Tuesday.

The prisoner, Elbert R. Barnes, 29, of Newport, was arraigned Tuesday in District Court on four felony counts of assault with a deadly weapon with intent to murder after the Monday night attack.

The officers were stabbed after being sent into the cellblock area at about 6 p.m. to calm Barnes, who had become violent, said Sgt. Francis Tessina, a police spokesman.

All four officers were treated and released from Newport Hospital, but none was able to return to duty, Tessina said.

Barnes allegedly used a weapon fashioned from pieces of metal and plastic ripped from a ventilation grate, police said.

Police Chief John C. Beebe III said an investigation is under way to determine how the prisoner could obtain the materials from the cell in the city's new $2.5 million police station. The police department moved to the new facility in April.

Barnes also was charged with three counts of assault and battery, and one count each of obstructing a police officer, malicious mischief and driving while intoxicated, all misdemeanors.

He pleaded innocent to the six misdemeanors before Judge Paul J. DelNero. No pleas are entered in District Court on felony charges.

Barnes was sent to the Adult Correctional Institutions in lieu of $140,000 bail, said clerk Francis Connelly. A pre-trial screening was set for Aug. 22.