MENDON (CBS) – Police said they know who planted two bottle bombs in Mendon over the weekend.

One bomb was found near a home on Park Street, while the other was thrown from a car on Route 16 right in front of the Alicante Restaurant. One of the workers there found the bomb and got rid of it just in time. No one was hurt.

Four 17-year-olds who are high school juniors were arrested in the case. Investigators say the bombs were made using chemicals and plastic bottles.

WBZ-TV’s Jonathan Elias reports.

It was a tip from a shopper at the Northbridge Walmart that called in the tip. Police say that shopper saw three of the teens buying just tinfoil and toilet bowl cleaner. The shopper knew those were ingredients to make home made bottle bombs, and after seeing the news and hearing about the reward she called it in.

Police say the four teens admitted to making and throwing the bombs and have apologized. Police Chief Ernest Horn says the four have been very cooperative and have been very honest about what they’ve done.

“Their intent was to create a practical joke and have some fun, obviously that didn’t happen,” said Horn.

The teens will have to answer to charges of disturbing the peace and throwing explosives.

WBZ-TV’s Jonathan Elias contributed to this report.