Tributes have poured in for a “loving” and “popular” young motorbike fan who was one of six people thought to have died after taking a class A substance in south Essex.

Friends of 20-year-old Cian Daly – who volunteered helping teach disabled children to fish – have set up a fundraising page to pay for a memorial bench at a nature reserve.

His family described Daly, from Leigh-on-Sea, as a “free spirit” in an emotional tribute. “Cian was very loving and always everyone’s best mate,” they said. “He was cheeky and popular, and everyone liked him.”

A keen sportsman, as well as a bike and car enthusiast, Daly will be honoured by friends later this month when they hold a “ride out” along Southend seafront in his memory.

He is the first to be named after a spate of deaths within a six-mile radius between Sunday and Tuesday. The deaths have prompted urgent warnings about the use of illegal substances.

The three men and three women were found dead in their own homes. Essex police are investigating which substance was responsible but have warned against speculation about a bad batch of drugs.

Daly, who went to Darlinghurst academy in Leigh-on-Sea and The Deanes school in Thundersley, was “really good” at athletics as a boy and played for a local football team, as well as attending cadets and a boxing club.

In a statement, his family said: “As he got older, he had a passion for motorbikes, cars and fishing. On his 16th birthday he got a moped … When his friends used to have problems with their bikes, they used to bring them round to the house and he would help fix them.

“Cian put 100% into everything and he could have done anything. He was the type of person who always had to be doing something, he wouldn’t just sit around.

“He lived a full and varied life, and he did that to the end. He was a bit of a free spirit and just wanted to help people. If anyone had a problem, he would drop everything for them.”

Daly’s friend Oliver Harwood, 23, posted a tribute on Facebook in which he described him as “one of the kindest people I know”.

Harwood said he felt numb after hearing the news that Daly – whom he nicknamed C-Dog – had died on Monday. “Not only was he one of the most clever people I know (he could strip a bike engine up and down for fun when he was 16) he was also one of the kindest people I know.

“He helped teach young and disabled children fishing, as well as be there for his friends 24/7. If you were ever in trouble, you KNEW Cian would be there for you, whatever the situation.

“I spent weeks/months on the bank fishing with you where we would just chat and chat about anything and everything – not a care in the world. You have no idea what I would do to do that with you again, my brother.”

The fundraising page for a memorial bench had received more than £2,000 in donations by Thursday afternoon.

The “ride out” along Southend’s seafront will take place on Saturday 10 August. A Facebook page for the event said: “He loved his bikes and cars and would’ve loved for this. Cars, bikes, and everyone else welcome. Let’s pack it out for him.”

On Monday, a woman in her 30s was found dead in Westcliff. The body of a woman in her 40s was found in Canvey Island on Tuesday, only hours after a man, also in his 40s, was found dead in the same town. A man in his 20s was also found dead in Benfleet. On Wednesday, police announced they had linked a further death to their investigation, that of a woman in her 30s, who was found in Southend on Sunday.

On Wednesday, Ch Supt Kevin Baldwin of Essex police said: “All of the deaths occurred in their own homes … The circumstances suggest that they weren’t able to call for assistance.”

Public Health England issued a warning urging drug users to be extra careful about what substances they take and to test a small amount first.

“They need to look out for each other and be alert to any signs of an overdose, such as lack of consciousness, shallow or no breathing, ‘snoring’, and blueing of the lips and fingertips,” PHE said. “They should immediately call for an ambulance and use any available naloxone if someone overdoses on opioids. We strongly advise all dependent drug users to get support from local drug services.”