Three people have died and more than 100 people are wounded after two explosions at the Boston Marathon. There are sites to help find the 374 British and 108 Irish runners that were expected to have taken part in the Boston Marathon.
The organisers of the London Marathon say they "fully expect" it to go ahead as planned on Sunday, although "security will be reviewed", after two explosions hit the Boston Marathon yesterday, although "security will be reviewed."
Vale of Glamorgan MP Alun Cairns is among the Welsh runners taking part, and has urged others to "turn out in confidence."
The head of crisis management department at the Foreign and Commonwealth Office has said a hotline number will remain open 24/7 to callers in the UK who are seeking information on loved ones in relation to the Boston bombings.