DEVELOPING STORY:

A Milwaukee prisoner on his way to the hospital is now on the loose after attacking an officer and escaping a police van, authorities told a local TV station.

Martin Williams, 22, fled Wednesday morning while he was being taken to St. Luke's Hospital on the city's south side to be fitted with a heart monitor, an official with the Milwaukee House of Corrections told WITI TV.

The officer was armed but no shots were fired, and he wasn't badly hurt in the scuffle that broke out just before 11 a.m., according to the station.

Williams, who is behind bars on armed robbery charges, reportedly got away on foot near the intersection of 35th Street and Kinnikinnick Avenue. He later shed his orange prison vest, WITI reported.

Williams allegedly attacked the guard as he was being escorted out of the vehicle, the station said. The manhunt caused Milwaukee police and sheriffs to block off roads while they were scouring the area with the help of K-9 units.

Williams is described as a Native American man weighing about 200 pounds with black hair and brown eyes. He was last seen wearing a grayish-white T-shirt, orange pants and black velcro tennis shoes, along with the orange vest he took off, Milwaukee police told FOX News.

Williams is a pre-trial detainee for armed robbery with threat of force, a crime he's been convicted of in the past, according to WITI. His trial is scheduled for October.

This is a developing story. Please refresh for updates.