NEW YORK (AP) _ Up to 40,000 construction workers strangled traffic today with a protest rally and march through midtown Manhattan, and some scuffled with police in riot gear.

The workers were angry over the awarding of a non-union contract for a transit project.

Nearly four hours into the demonstration, about half a dozen workers were arrested when they tried to turn over a parked van. Some of them said police used pepper spray before handcuffing them and putting them in a police van.

The crowd shouted ``police state'' when dozens of officers with nightsticks came to break up the crowd. There was shoving and bottle-throwing, and some officers used nightsticks to control the crowd.

There were 23 civilians and 10 officers injured, apparently none seriously, authorities said.

Mayor Rudolph Giuliani said the crowd numbered about 40,000 at its peak, but Police Commissioner Howard Safir late put the number at 20,000 to 30,000. Some shops and offices were forced to open late because their employees couldn't get to work through the crowd.

The demonstrators accused the MTA of awarding work to a contractor who used nonunion help. They said the contractor had violated safety regulations, too. Some displayed a 10-foot inflatable rat, symbolizing what they called rat contractors.

``They're taking food from union families. We want to make sure we get the right attention,'' said electrician Joe Solano of Brooklyn.

MTA spokesman Tom Kelly said the contract was awarded ``to the lowest responsible bidder in accordance with law.'' He said aspects of the contract were being investigated by the state Department of Labor.

Giuliani, who blocked a protest by taxi drivers in May by arguing that they were trying to shut down the city, said officials were surprised by the size of the construction workers' protest.

``Had the construction workers given the same advance warning that the taxi drivers gave, they'd have been dealt with in the same way,'' he said.