Two dolphins were found dead with similar injuries within one week along Florida's gulf coast, prompting investigators to offer a reward of $54,000 (£42,000) for information.

Biologists with the Florida Fish and Wildlife Conservation Commission (FWC) discovered a dead dolphin off Naples in southwest Florida last month. The porpoise had been killed by a bullet or sharp object, investigators said.

The same week, Emerald Coast Wildlife Refuge experts recovered a dolphin along Pensacola Beach in the Florida Panhandle. A bullet was found lodged in the side of the marine mammal.

The National Oceanic and Atmospheric Administration (NOAA) first offered a $20,000 (£15,600) reward last month before raising the amount to $54,000 on Monday in combination with money pledged by animal rights groups.

Experts believe the two deaths might have stemmed from humans feeding the animals. When dolphins learn to associate people and boats with food, they can expose themselves to dangerous situations.

Tragic photos show beached whales Show all 15 1 /15 Tragic photos show beached whales Tragic photos show beached whales A dead sperm whale lies on Hunstanton beach in Norfolk on 5 February 2016 AFP/Getty Tragic photos show beached whales Volunteers pour buckets of water over the 80 remaining live pilot whales found stranded on remote Ocean Beach on New Zealand's southern-most Stewart island, 8 January 2003 AFP/Getty Tragic photos show beached whales Contractors clear away the body of one of the dead 48ft sperm whales that were washed-up on a beach near Gibraltar Point in Skegness, Lincolnshire in 2016 PA Tragic photos show beached whales People pass by a beached whale at the Pointe de la Torche, near Brest in France on 29 November 2011 AFP/Getty Tragic photos show beached whales A woman touches the tail of a large whale carcass on Wattamola Beach at the Royal National Park in Sydney on 25 September 2018 AFP/Getty Tragic photos show beached whales Beached humpback whale in California, 2015 AFP/Getty Tragic photos show beached whales Dead long fin pilot whales at Hamelin Bay on Australia's west coast on 23 March 2009 AFP/Getty Tragic photos show beached whales A 36ft sperm whale lies dead on the beach at Sutton Bridge, in The Wash, off the Lincolnshire coast, where it became stranded in 2004 PA Tragic photos show beached whales A female fin whale opens its mouth as it lies stranded and alive on the beach at Carlyon Bay, Cornwall on 13 August 2012 Getty Tragic photos show beached whales The lower jaw of a dead sperm whale that stranded itself on a beach in Hunstanton, Norfolk on 5 February 2016 Getty Tragic photos show beached whales One of the five sperm whales that were found washed ashore on beaches near Skegness, Lincolnshire over the weekend on 25 January 2016 Getty Tragic photos show beached whales Employees at work to skin the remains of a beached 60ft whale on 25 January 2013 AFP/Getty Tragic photos show beached whales Two long-finned pilot whales are stranded on a beach in the northern French city of Calais on 2 November 2015 AFP/Getty Tragic photos show beached whales A sperm whale lies dead after becoming stranded on a beach in Hunstanton, Norfolk on 5 February 2016 Getty Tragic photos show beached whales Crowds gather as a sperm whale lies dead after becoming stranded on a beach in Hunstanton, Norfolk on 5 February 2016 Getty

The NOAA urges people to not feed wild dolphins.

It is a crime in the US to harass, hunt or feed wild dolphins under the Marine Mammal Protection Act. Offences can be punished by up to $100,000 (£78,000) in fines and up to one year in prison.

Since 2002, at least 29 dolphins have washed up on the southeast US coast with evidence of being shot by guns or arrows, or impaled with objects such as fishing spears. In May 2019, a dolphin was found dead off Captiva Island with a fatal puncture wound to its head. An investigation into that death is still ongoing.