"Our deepest condolences go out to the family of the worker who has been tragically killed today.
Crossrail's contractor BFK has some serious questions to answer.
Unite is particularly concerned about health and safety at the site because this is not the first serious incident.
In December 2012, a worker sustained horrific burns when he cut through a cable.
We now expect BFK to meet with Unite as a matter of urgency.
The contractor must explain how it intends to do everything in its power to ensure that a tragic incident like this does not happen again."
"We expect the coalition Government to pay special attention to this tragic incident.
Since the Government took power, there have been constant attacks on safety laws and regulations.
The Government should be strengthening health and safety laws, not weakening them."
More top news
Police investigating the murder of a grandfather from West Ham have arrested a second man on suspicion of murder.
Police are appealing for information after a woman was killed and three people injured after a crash in east London.
A restaurant where pets and their owners can share a meal together has opened just in time for Valentine's Day.