1.  The men, who work for the Ambassador Bridge Corp., had been painting the privately owned bridge when it fell.

2.  The men, who work for the Ambassador Bridge Corp., had been painting the privately owned bridge.

3.  The men, who work for the Ambassador Bridge Corp., had been painting the privately owned bridge when the scaffold collapsed.

4.  The men, who work for the Ambassador Bridge Corp., had been painting the privately owned bridge when their scaffold collapsed.