Police in the Mexican state of Sonora say they fought a pitched three-hour battle to free a border rail crossing at Nogales that had been blocked by people protesting a gasoline price increase.
The Sonora state government says two police officers were injured and two protesters were arrested Sunday.
The demonstrators were protesting a recent 20-percent hike in gasoline prices.
The state government said officers who tried break up the blockade were attacked with rocks for about three hours and responded by "firing rubber bullets into the air."
The government said 11 trainloads with about 1,000 cars of merchandise headed for the United States had been backed up by the protest.
It said the blockade had threatened to temporarily shut down Ford Motor Co.'s stamping and assembly plant in Hermosillo.