More than 50 firefighters from 15 stations across the county have spent the last few hours tackling the blaze.
Part of the tower where the fire broke out has collapsed.
A spokeswoman for SSE, which runs the power station, said: “At around 2pm today a serious incident occurred at SSE’s Ferrybridge C power station in West Yorkshire.
The company’s practised emergency response procedures have been activated. West Yorkshire Fire and Rescue Service are in attendance and dealing with the incident with assistance from expert engineers on site. All personnel have been accounted for and no injuries have been reported at this stage.
“It is too early to give any more information regarding this incident; however, we will issue a further statement when more details become available. Our immediate priorities are to deal with the incident and to ensure the safety of staff, contractors and the general public.”
The fire had no impact on electricity supply as the plant was on summer shut down, a National Grid spokeswoman said.
She said: “They were not generating onto the grid so it is not going to affect our operations at all.”
Roads around the site were closed but the nearby M62 motorway and A1 remained open.
Normanton, Pontefract and Castleford MP Yvette Cooper said: “The firefighters, emergency services and experts on the sight have done an incredible job getting this awful fire under control - and thanks must go to all those who’ve risked their own safety in tackling the blaze.
“I’m incredibly relieved at the news no one has been hurt. Ferrybridge and Knottingley are tight knit communities and I know everyone will have been deeply concerned about the staff and emergency services on the site.
“Ferrybridge power station is a really important local employer, and is a significant part of our national energy infrastructure. So everyone is of course worried about the scale of the damage, and will want to support the SSE workforce as they do a full assessment of the plant once the site has been made completely safe.”