Police want to identify a man seen after a series of racist stickers were placed on trains in Southend.
A CCTV image of a man has been released following the discovery last month, and officers urge anyone who recognises him to get in contact.
PC Maria Wheele said: "Rail staff cleaning trains the week of Sunday, 18th January found stickers carrying offensive messages. Passengers travelling between Essex and London that week might have seen something.
"If anyone recognises the man in the CCTV image, please contact us."
Essex Police say that they can't comment on Martin Goldberg's death, but there were indications of an attempt to destroy evidence.Read the full story ›
Police say indecent images of children have been found at the home of a deputy head teacher, who was recently found dead.Read the full story ›
A police helpline has been set up for any concerned pupils or parents. The number to call is 0800 056 0944, or +44 207 158 0010 for anyone living outside of the UK.
Police were told about allegations against a deputy headteacher nine months before they first spoke to him, the Essex Police and Crime Commissioner has claimed.
Martin Goldberg, a Maths teacher at Thorpe Hill school in Southend, was found dead at his home on September 10 - just a day after police spoke to him about claims he bought images of naked teenage boys over the internet.
Police subsequently found nearly 600 indecent images of pupils on his computer, with many showing children as young as nine undressing in changing rooms.
Nick Alston said his initial judgement was that something had gone "badly wrong", adding that aspects of the case had been referred to the Independent Police Complaints Commission.
"I understand the original information from police in Toronto suggesting that Goldberg had purchased videos of naked boys several years ago was received by Essex Police in late November 2013," Alston said.
"The Police Online Investigation Team first visited Goldberg on September 9, 2014. It is important that we understand why it took nine months for the force to act on this information. There may be valid reasons but we deserve an explanation."
A former Thorpe Hall pupil has told ITV News the school's deputy headteacher "fooled us all", amid allegations he stored nearly 600 indecent images of children as young as nine.
Ex-maths teacher Martin Goldberg, 46, was found dead at his Essex home just a day after police had spoken to him about claims he bought images of naked teenage boys over the internet.
"He fooled us all. Pupils and staff. He was always friendly with pupils but then all teachers were," the ex-pupil said.
"Only sense of weirdness was just the usual - I thought he was bit lonely and sad and had no life outside of school.
"His life revolved around school. He was an OK teacher, very very involved with ski trips and extra-curricular stuff."
Essex Police says it currently has no evidence to suggest a former deputy headteacher - who stored hundreds of indecent images of pupils - made "inappropriate physical contact" with any child.
It is important to stress that we have found no evidence of any other offences by Mr Goldberg involving these children. At this time there is nothing to suggest that he made inappropriate physical contact with any child.
There is also no information that he shared any of these images or that anyone else was aware of his offending.
Essex Police understands that this news may be extremely distressing to both parents and children and has set up a special number for people to call if they have any concerns or believe they have information that would assist the investigation.
Nearly 600 images found on the computer of a deputy head of an Essex school are believed to be of boys aged from nine to 12.
Essex Police believe the images - which were reportedly taken from 2000 onwards - were taken on a camera hidden inside a bag belonging to Martin Goldberg.
Seventy-five images were taken in Thorpe Hall's male changing rooms, with 465 others taken in a local swimming pool and 38 from two other locations.