An investigation has been launched after a railway worker was hit by a Met Line train.

The Rail Accident Investigation Branch (RAIB) says the woman was struck near Chalfont & Latimer station at around 9.30am on April 15 by a train travelling at around 25mmph.

She was taken to hospital but the British Transport Police said her injuries were not deemed to be life-changing or life-threatening.

A team of inspectors were sent down to the Buckinghamshire site to gather information and determine whether an investigation into what happened is necessary.

Giving further details about the incident, the RAIB said: "The train involved, which was a London Underground Metropolitan line service from Baker Street to Chesham, was travelling at around 25 mph (40 km/h) on a section of track used by trains running in both directions, where the maximum permitted speed is 35 mph (56 km/h). There are two other running lines at this location.

"The track worker was part of a group of three staff who were undertaking a scheduled track inspection. This was planned to take place while lines were open to traffic and with a system of work in place intended to keep staff away from moving trains."

The incident blocked all lines, affecting Met Line and mainline Chiltern Railway services running through Rickmansworth and surround villages.

It has now been confirmed a full investigation into the incident will take place by the RAIB.

A spokesperson said: "Our investigation will aim to identify the sequence of events which led to the accident and will include consideration of the actions of those involved, the planned system of work, the arrangements in place for planning work where lines are open to traffic, the management of the competence of track workers, and any relevant underlying factors.

"Our investigation is independent of any investigation by the railway industry or by the industry’s regulator, the Office of Rail and Road.

"We will publish our findings, including any recommendations to improve safety, at the conclusion of our investigation."

Transport for London has also launched its own investigation.

Lilli Matson, chief safety health and environment officer said: "Safety is our top priority so we were extremely concerned by this serious incident. Fortunately no significant injuries resulted. Our thoughts are with those involved.

"As normal with an incident on the railway, the Office of Rail and Road (ORR) and the Rail Accident Investigation Branch will be undertaking an investigation to identify the cause of the accident and make recommendations.

"In addition to assisting the ORR and RAIB, we will be undertaking our own formal investigation."