MINNEAPOLIS, Aug 1 (Reuters) - A bridge carrying a four-lane state highway across the Mississippi river in central Minneapolis collapsed during rush hour on Wednesday, plunging cars and trucks into the river. The bridge carrying Route 35W, which was under repair, buckled and fell into the river at about 6:10 p.m. CDT (2310 GMT), local media reported. Witnesses said they heard a rumbling sound as the bridge collapsed into the river. Local media reported 20 to 30 injuries but initially no deaths. "First I heard this huge roar," Leone Carstens, a nearby resident, told the Minneapolis Star Tribune. "I was at my computer. Initially I thought, Wow was that an airplane?" Television pictures showed sections of highway leading to the bridge had also collapsed, in places crushing cars and starting fires and trucks. One witness said she saw people swimming in the water seeking safety. Huge chunks of the bridge stuck at odd angles out of the river, in places surrounded by cars half submerged in the water. A nursing supervisor at Hennepin county medical center interviewed by local WCCO radio said, "We have multiple patients. Some critical, some non-critical," he said. Asked if there were any deaths, he said: "Not that I know of." The road was carrying bumper to bumper traffic when the 500-foot (160 metres) steel arch bridge collapsed. The bridge, built in 1967, was 64 feet above the river. source-http://www.reuters.com/article/bondsNews/idUSN0140206320070802