The police suspects that an acute financial crunch is the reason behind their extreme step.
The deceased were identified as Arvind Gohil (42), his wife Naina (38), son Mitul (9) and daughter Kamini (6).
According to the Khambhat rural police, Arvind was a mason and used to live with his family at Bhadran village of Borsad taluka here.
Yesterday afternoon, Arvind came to Ralaj village with his family and visited a temple.
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Later, all of them were sent to SS Hospital in the nearby Petlad town.
Arvind and his daughter Kamini died on the way, while his wife Naina and her son Mitul were referred to the SSG Hospital in Vadodara.
"However, they also died today morning. Our primary investigation revealed that the Gohil family faced an acute financial crunch, which may have forced them to commit suicide," a police official said.