The crews were called to three separate fires on Saturday and again on Sunday to fires involving trees along the river, all of which were started deliberately. Watch Commander Gareth Boyd said: While it may be seen as simply a tree on fire, it takes a substantial amount of effort to put these fires out. Each of these incidents took around an hour to resolve, ensuring the surrounding area was left safe and damping it down. Deliberate fires such as these can not only get out of control and spread very quickly, but they also potentially take us away from other emergency situations. One of the incidents in particular involved an old tree that could have easily collapsed, which could have not only made the fire spread but also seriously injure a member of the public or a firefighter. The fires are being treated as arson. Anyone that may have seen anything should contact police on 101 or Crimestoppers on 0800 555111 to report the information. Group commander Kevin Napier, head of community fire safety, said: The people responsible may think that what they are doing is just a bit of fun, but they need to realise there are serious consequences of deliberate fire setting. Fire can spread quickly and someone may get seriously injured or killed as a result of their actions. Also if our crews are having to attend deliberate nuisance fires like these, they may get delayed attending a real emergency where someones life is at risk and it could be one of their friends or family members.The incidents that happened over the weekend were: Saturday, 8.24am - small fire involving a tree near rowing boat club, in Hartford Road Saturday, 2.37pm - trees on fire in Riverside Park, Hartford Road Saturday, 3.20pm - tree on fire in Hartford Road Sunday, 1.02pm - tree on fire in Main Street, Hartford.