Fifteen persons from Bihar, including four children, were killed and two were injured here Saturday when a portion of a 22-ft high compound wall of a housing society collapsed on adjoining shanties of construction workers following incessant rains.

The police registered a case of culpable homicide against directors of two construction firms, and arrested two builders.

While the Maharashtra government announced compensation of Rs 5 lakh for the kin of the deceased, Bihar Chief Minister Nitish Kumar announced ex-gratia of Rs 2 lakh.

"We have arrested Vipul Agarwal and Vivek Agarwal of Alcon Landmark," said Anil Patil, senior police inspector, Kondhwa Police Station. The firm had constructed Alcon Stylus, the housing society whose wall collapsed.

The incident took place between 1:30 am and 1:45 am in Kondhwa. The victims were living in makeshift shanties next to Alcon Stylus.

On the adjacent plot, excavation was going on for under-construction Kanchan Royal Exotica building. Municipal Commissioner Saurabh Rao said it appeared the soil was loosened due to heavy rain and the excavation which was carried out "irresponsibly" close to the compound wall.

The tragedy was aggravated as cars parked along the wall inside Alcon Stylus society fell on the shanties as part of the ground caved in. The shanties were at a lower level than the building wall because of the excavation.

Pune city received 73.1 millimetres of rain Friday, the second highest rainfall in June since 2010.

Fifteen people died and three were rescued, out of which two were undergoing treatment, officials said.

Expressing grief over loss of life, Chief Minister Devendra Fadnavis ordered an inquiry. The state government also announced compensation of Rs 5 lakh each for the kin of the deceased.

Commissioner Rao said there was a landslide in which the 20-22 feet wall caved in and fell on the shanties.

"According to preliminary investigation, deep excavation was being carried out in an irresponsible manner. The digging work was going on almost near the wall," he said.

A five-member committee of an additional collector, officials of Building Permission department of the corporation, labour department and a structural expert from the Government College of Engineering will probe the incident, he said.

"The committee will submit its report in the next seven days, and action will be taken against those responsible for the mishap as per findings of the report," he said.

Chief minister Fadnavis said on Twitter that he was "extremely saddened" by the loss of life and and he had directed Pune Collector to conduct an "in-depth enquiry".

Governor Ch Vidyasagar Rao also expressed grief. "Every life lost in incident was precious," he said in a statement.

State Congress chief Ashok Chavan urged the government to extend all help to families of the dead and injured.

The deceased were identified as Alok Sharma (28), Mohan Sharma (24), Aman Sharma (19), Ravi sharma (19), Laxmikant Sahani (33), Sunil Singh (35), Ovi Das (2), Sonali Das (6), Bhima Das (38), Sangita Devi (26), Ajit Kumar Sharma (7), Rekhal Kumar Sharma (5), Niva Devi (30), Dipranjan Sharma and Avdesh Singh.

All of them were from Barsoi sub-division of Katihar district in Bihar. Bihar Chief Minister Nitish Kumar expressed "deep sorrow" over the tragedy and ordered ex-gratia for victims.

Arrangements will be made to bring the bodies back by air ambulance, Bihar officials said.

Pune police registered a case of culpable homicide not amounting to murder under IPC section 304 against Jagdishprasad Agarwal (64), Sachin Agarwal (34), Rajesh Agarwal (27), Vivek Agarwal (21) and Vipul Agarwal (21) of Alcon Landmarks, and Pankaj Vora, Suresh Shah and Rashmikant Gandhi of the Kanchan Royal Exotica project.

Residents of Alcon Stylus society alleged that they had warned the builder about the compound wall being in bad shape and tilting outward as back as February, but no steps were taken to fortify it