According to witnesses, several police cars are parked in the village, with the air ambulance landing nearby. One said there was possibly 20 to 30 emergency vehicles at the scene. A smaller cordon has been set up within the larger cordon on Baglan Street.
Another witness told WalesOnline: “I can count six ambulances, eight police cars and four first responders.”
Rhondda MP Chris Bryant said: “I have been informed that the incident in Ynyswen is a major incident.
“The emergency services will be in attendance for a very long period of time.
“Please do avoid the area. I sincerely hope nobody is extremely hurt.”
South Wales Police confirmed they were dealing with a “serious incident” which involves a “number of casualties”.
A spokesman said: “Police units are currently dealing with a serious incident which occurred in Baglan Street, Treorchy, at around midday today.
“Ambulance crews are also in attendance as the incident involves a number of casualties.
“The street has been closed off and people are advised to avoid the area until further notice.”
One person at the scene said they had never seen a police presence like it before.
They said: “I’ve never seen a police presence like this before.
“It’s clearly a major incident.”
It is believed officers are carrying out investigations along Baglan Street.
More to follow…