The building houses MTNL's telephone exchange.
Internet and telephone services in Mumbai's suburban Bandra and nearby areas were affected due to the massive fire at the MTNL building, the state-run telecom company said on Tuesday.
The company said efforts were on to restore the services affected due to the cables and other equipment getting burnt in the fire in the nine-storey Mahanagar Telephone Nigam Ltd's (MTNL) building on Monday.
The building houses MTNL's telephone exchange.
"Due to the fire in the building, the telephone and internet services of customers in Bandra Reclamation, Kalanagar, Kherwadi, Pali Hill and some other surrounding areas have been affected," the MTNL said in a statement.
"The services are likely to be restored in seven to eight days."
The fire broke out at the building on Monday afternoon and up to 100 people, 84 of them stranded on its terrace, were rescued in one of the biggest operations in recent times, Mumbai fire brigade chief P S Rahangdale said.
Over two dozen machines and equipment, including fire engines, special hydraulic ladders, jumbo water tankers, robofire (a robot), rescue van and breathing set vans, were used for the rescue operation that lasted for several hours, he said.
A fire brigade team was still carrying out cooling operations, another official said, adding they hope to complete the exercise by evening.
The fire was confined to office cabins, records, furniture, computers, server room, wooden racks, windows, doors, UPS batteries, electrical wirings and switch gears, among others, on the second, third, fifth, seventh and eighth floors, Mr Rahangdale said.
"Though the fire was brought under control on Monday evening, the cooling operations are still underway to ward off the smoke and eliminate any chances of a blaze," he said.
"I am happy to see that everything went well during the rescue operation," the official said.
Asked why the robot deployed at the site did not perform as expected, he said it did a "satisfactory" job.
"The robot's job was quite satisfactory. Its handler did not get enough space to manoeuvre it," he added.