It was just before 3 a.m. Tuesday and still dark on Hwy. 55 in Eagan, when the 3-year-old boy wearing nothing but a red T-shirt -- no shoes, no pants, no underwear -- started across the highway.

Leslie Petroff and her husband, Phil Alexander, bleary-eyed after driving back from their northern Minnesota cabin, saw a tiny bit of red out of the corners of their eyes.

"Phil said, 'Oh my God, there's a little boy crossing the road,'" Petroff said. "I said, 'I know -- stop the car.'"

It turns out the half-naked boy had soundlessly left the two-story townhouse where his family was visiting -- going down two flights of stairs, entering the garage, pushing the opener button and walking out, police recounted later.

He went across a buffer zone of grass and wildflowers to reach the intersection of Lone Oak Road and Hwy. 55 nearly a half-mile away.

As Alexander called 911, Petroff got out and dashed across the road. She scooped up the boy and returned to the car, where they waited for police.

"That shirt saved him," she said. "He could have easily been hit by a tired trucker, or worse."

She added: "I think he was sleepwalking. As soon as I picked him up and put him on my lap in my car, he fell asleep."

His parents, police said, were asleep and had no clue he was missing. They first noticed he was gone shortly after 5 a.m., police said. By then, Eagan police had taken him into protective custody after checking at area hotels and gas stations to see if anyone in the area had lost him.

Neighbors, who didn't give their names, said they heard the child's mother, noticeably shaken, calling his name around 5:15 a.m. as she walked up and down the block.

Police said the mother and child were not residents but were staying there overnight.

The mother, who could not be reached for comment, called police about 5:30 a.m. and discovered her son was safe.

As of Tuesday afternoon, police said, the boy was in the custody of social services workers on a 72-hour health and welfare hold.

However, a police spokeswoman said there is no evidence of neglect or trouble in the home, and no charges are expected.

Because their investigation is continuing, police said they would release no more information Tuesday.

The names of the boy and his parents were not released.

Late Tuesday afternoon, as her husband slept at the couple's Bloomington home, Petroff took a break from her gardening to reflect on the panic the family must had felt. She also marveled at the boy's -- and his parents' -- good fortune.

She and her husband were exhausted when they spotted the toddler, she said. They had been awake since 7 the morning before and had been driving much of the day back from their cabin near Cotton, Minn. If they hadn't just gassed up at the Kwik Trip a block away, Petroff said, they might never have noticed that tiny bit of red on an otherwise dark highway. Traffic was picking up, and trucks were already starting to speed by, she said.

"It scared me," she said. "My adrenaline started going. I couldn't believe it. I'm glad we saw him."

Alex Ebert • 612-673-4264 alex.ebert@startribune.com James Walsh • 612-673-7428 james.walsh@startribune.com