Mumbai: At least 13 persons have perished in different incidents, mostly by drowning, in the first monsoon weekend in the past 72 hours. Five persons, including four of a family, from the Immaculate Conception Colony in Borivali drowned at a beach picnic in Ratnagiri on Sunday afternoon.

They are Monica D'Souza, 44, Sanomi D'Souza, 22, Richa D'Souza, 19, and Mathew D'Souza, 18, besides their neighbour and family friend Kenneth Masters, 56.

The incident occurred at the small Aare-Ware Beach near Devrukh in Ratnagiri when they were en route to famed Ganpatipule.

Apparently ignoring Met warnings, the victims ventured into the choppy waters, but were trapped in a sudden whirlpool that built up at an intersection in the Arabian Sea and a creek along the beach.

Their bodies were likely to reach Mumbai on Monday for the last rites in Borivali West's IC Colony which plunged into a pall of gloom.

Two Thane cousins -- Anand Gupta and Nandini Gupta -- drowned when they accidentally walked into a ditch full of water, which was dug up to lay a sewage pipeline, on Sunday.

There were no warning indicators near the ditch excavated near a road by a private contractor appointed by the Thane Municipal Corporation.

In another weekend tragedy, three youths drowned in two separate incidents at the Bhuigaon Beach in Palghar district on Saturday evening.

While the bodies of two -- Rahul Rathod, 18, and Abhivan Shinde, 17, -- washed ashore at Kalamb Beach near Vasai, efforts were on to trace the third, police said.

Police suspect that the youth may have been pulled away by the thick under currents in the Arabian Sea as monsoon is round the corner, roughing up the sea on the entire western coast.

Besides, three persons were electrocuted in two separate incidents in Bhandup after the city and surroundings were lashed by sudden thunderstorms on Saturday evening, marking the onset of the monsoon season.