Rescuers Tuesday began a second day of searching for a Brigham Young University student apparently lost on Y Mountain.

Aaron Steven Lowe, 25, a Woodbury, Minn. native, hasn't been heard from since Sunday at 3 p.m. when he called his wife from the mountain on a cellular telephone. Lowe told her he would call back later to be picked up.The Provo Police Mountain Rescue Team and the Utah County Search and Rescue Team spent all day Monday scouring the mountain, without finding any sign of Lowe. A Utah Highway Patrol helicopter equipped with an infrared camera joined the search Tuesday morning.

"We are concerned that perhaps he's fallen and been injured," said Provo police spokeswoman Karen Mayne. "We are staying as upbeat as possible."

Lowe was wearing a T-shirt and carrying a backpack with sandwiches when he left on the hike Sunday afternoon.