A 9-year-old autistic boy was struck and seriously injured by a truck early yesterday after he wandered into traffic on Route 29 in the White Oak area of Silver Spring, police said.

Desmond Akyea of Featherwood Court in Silver Spring unlocked the front door to his home about 4 a.m. and wandered outside, police determined.

The driver, Teodoro Matiga, 36, was heading south on Route 29. He told police that he spotted Desmond in the middle of the road near Industrial Parkway and tried to swerve to avoid hitting him but that the boy jumped into the same lane.

Desmond's mother approached police at the scene of the accident and identified her son. About the same time, police got a call for a critical missing person from Desmond's father.

Desmond is in an area hospital in serious but stable condition, authorities said.

Neither Matiga nor Desmond's family could be reached for comment.

Police have not filed charges against Matiga, of the 4600 block of Waterfall Court in Owings Mills. The investigation continues.

The accident marks the second serious incident involving an autistic child in Montgomery County in recent weeks.

On June 23, a 4-year-old girl died after falling out a window of her family's 10th-floor apartment in Silver Spring.