UXBRIDGE - Six puppies found Sunday in the Blackstone River, tied in a grain sack, had a guardian angel looking over them, Police Chief Jeffrey A. Lourie said at a news conference Monday at the police station.

Kayakers on the river heard whimpering and found the discarded puppies, partially submerged. One of the kayakers called police around 1 p.m., and immediately regional Animal Control Officer Kevin Sullivan responded and started to provide medical care.

One of the animals, the runt of the litter, was at the bottom of the puppy pile and had taken fluid into its lungs, which it eventually expelled. The pups, which are believed to be a Labrador mix and are about four or five days old, are being cared for and bottle-fed at Mr. Sullivan's home. They were examined by a veterinarian Monday and are expected to recover.

Chief Lourie said investigators are trying to identify the person responsible for dumping the dogs.

He said police would like to speak with a white man seen on a mountain bike near the area off River Road around the time they believe the crime occurred, between 11:30 a.m. and 1 p.m. Sunday. The man may have witnessed something, police said.

"In more than 29 years ... I've seen several cruelty to animal cases," Chief Lourie said. "I can never recall six newborn puppies being discarded into the river like this."

He said a suspect would be charged with six counts of animal cruelty.

The other task, according to the chief, is to "find them good forever homes." He said the Police Department has received a lot of calls regarding adoption.

Word about the bundle of discarded puppies spread widely across social media since Sunday. Uxbridge police asked anyone with information to call them at (508) 278-7755.

Chief Lourie said people also have asked about making donations. He is encouraging them to contribute to Uxbridge Regional Animal Control, which serves Uxbridge, Douglas and Mendon. The money will be used to help pay for the care of the puppies and other rescued animals. Checks for regional animal control can be sent to 275 Douglas St., Uxbridge, MA 01569.

Police declined to identify the kayakers who alerted police to the puppies in the river, saying they asked for privacy.

"They're just happy they were able to save the dogs," Chief Lourie said.