Not only did the bombing cause damage, so did pollution, according to Reuters.
There is also broken glass in the clock dials and a clock expert will be needed to get it in working order.
The BBC said all 1,296 pieces of glass that make up the clock's four dials will need replacing.
Since workers discovered additional damage, the cost to restore the tower and clock rose by about $25 million, Reuters reported.
The cost to fully restore Elizabeth Tower and Big Ben will be about $104.4 million, which will have to be approved by the accounting officers in Parliament, the BBC reported.
The restoration started in 2017 and was expected to continue until 2021.