Debra Denison, 47, and her two grandchildren, Alton Perry, 2, and Ashton Perry, 6 months, were found Tuesday evening in a minivan near Lake of Isle near Preston, Conn., Connecticut state Police Lt. Paul Vance told ABC News.
The boys' mother reported the three missing after Denison never returned from picking up the boys from day care in Danielson, a news release from state police said.
Police said Denison was bipolar, though would provide no further details in the case, including the causes of deaths.
Police said they planned to conduct autopsies Wednesday, ABC News reported.
2014: The Year in Music [PHOTOS]