RENEE MONTAGNE, HOST:
Let's go now to St. Paul, which has plenty of icy water to hear the spooky sound of winter turning into spring. Here's Minnesota Public Radio's Tim Nelson.
TIM NELSON, BYLINE: It started about 4 o'clock in the morning. It was a howl. Or a screech. Or a scrape, depending on who you asked. Here's what it sounded like.
(SOUNDBITE OF HOWL)
NELSON: Rachel Barth lives on the east bank of the Mississippi, near where it joins the Minnesota River.
RACHEL BARTH: It was like what a whale would sound like, which obviously there's no whales on land, combined with like a howling of a coyote or something like that. But it was really, really loud.
NELSON: Barth says even her dog was scared to go outside. Jeff Zaayer, who lives a few blocks away, thought it was a dog.
JEFF ZAAYER: I thought it sounded a little bit like a hound dog or something whining.
NELSON: Police drove around to investigate and ruled out a light rail train and a nearby construction project. The shipping season won't open again for weeks. The Army Corps of Engineers sent a sample of the sound to the cold region's research and engineering lab in Hanover, New Hampshire. They suspect the eerie sound is the ice on the Mississippi from the coldest Minnesota winter in 32 years slowly and noisily giving way. For NPR News, I'm Tim Nelson in St. Paul. Transcript provided by NPR, Copyright NPR.