San Antonio police detained a man who may have been intoxicated when he crashed into a 30-year-old cyclist just south of downtown Sunday evening.

Just before 7 p.m., a 52-year-old man driving a pickup was headed south on South Alamo Street when he attempted to turn left on South Presa, police said. He had a green light, but reportedly failed to yield while turning to two cyclists, who were riding north on South Alamo Street.

The front of the pickup struck one of the riders, who wasn't wearing a helmet, said police Sgt. Jim Prendergast. Police detained the motorist, who refused to give a breathalyzer test.

“He will be given a blood draw, based on the totality of the circumstances,” said Prendergast, adding that the cyclist suffered life-threatening injuries. The cyclist was taken to San Antonio Military Medical Center.

Twitter: @EvaRuth