A Key Peninsula Fire Department vehicle was involved in a collision near the intersection of Key Peninsula Highway and Cornwall around midnight.
The command vehicle was en route to assist a crew on a medical call when another vehicle crossed over the lane, striking the command vehicle.
Two people in the oncoming vehicle and one fire department employee were transported to Tacoma Hospital.
The fire department employees' injuries are not life-threatening, Fire Chief Tom Lique told KIRO 7 Eyewitness News.
The two others injuries are severe, but do not appear to be life-threatening.