Almost a third of house fires in Cleveland last year were started deliberately, figures from the Home Office show.
The numbers reveal the scale of the problem faced by Cleveland Fire Brigade, which tackled 70 incidents of arson last year - 31% of all the house fires in the area.
Since 2013, four people have been killed in arson attacks.
In total, 12 people lost their lives in incidents attended by fire services over the last five years.
In the 12 months to September 2017 alone, the most recent data available, two died. There were also 32 casualties, including 18 people who were taken to hospital as a result of their injuries.
In County Durham, the figures County Durham and Darlington Fire and Rescue Service tackled 65 incidents of arson last year - 24% of all the house fires in the area.
Since 2013, one person has been killed in an arson attack.
In total, 15 people lost their lives in incidents attended by fire services over the last five years.
In the 12 months to September 2017 alone, the most recent data available, zero died. There were also 86 casualties, including 41 people who were taken to hospital as a result of their injuries.
Dave Green, national officer at the Fire Brigades Union, said: “Starting fires deliberately in the home is a heinous crime. Rightfully, it is a serious criminal offence punishable by law. Arsonists do not just put the immediate victims at risk; they put whole communities and firefighters themselves in jeopardy.
“The fire and rescue service is already stretched to the limit in the fire cover they can provide. If firefighters are dealing with an arson at the same time as another fire call comes in, then those other victims are looking at a long wait before we can get to them.”
Across England, 346 people lost their lives in fires between October 2016 and September 2017, including 47 in deliberately started fires. The Grenfell Tower fire in Kensington in June 2017, which claimed 71 lives, meant the figure was the highest for any 12-month period since the data was first recorded in 2009.