Prosecutors have dropped charges against Adnan Syed – the subject of the hit podcast Serial – three weeks after his murder conviction was overturned.

It follows a further round of DNA testing, a lawyer with knowledge of proceedings said.

Mr Syed, now 41, was sentenced to life in prison in 2000 for the alleged murder of his girlfriend Hae Min Lee. He was 18 at the time.

A judge in Baltimore overturned his conviction on 19 September after prosecutors said two other possible suspects had not been disclosed to the defence at trial.

After being released, Mr Syed was placed in house detention with GPS monitoring.

Circuit Judge Melissa Phinn gave prosecutors 30 days to retry him or drop the charges.

On Tuesday, the city of Baltimore’s state’s attorney’s office confirmed it had dropped its case against him.

Lawyer Laura Nirider, who accompanied Mr Syed when he walked out of prison last month, said he had been “formally exonerated”.

Ms Nirider, co-director of the Center on Wrongful Convictions at Northwestern Pritzker School of Law, tweeted: “Breaking news: After the latest round of DNA testing generated results that, like previous rounds of testing, excluded Adnan Syed, he has now been formally exonerated!”

Last week, court papers were filed supporting an appeal by Ms Lee’s family.

While they are not challenging Mr Syed’s release, they want the judge to hold another hearing to enable them to address the court, lawyer Steve Kelly said.

Mr Syed, who has maintained his innocence for decades, came to public attention in 2014 during the debut season of Serial.

Doubts were raised about some of the evidence used in his case, including data from mobile phone masts.

The additional suspects were known at the time of the original investigation and were not properly ruled out nor disclosed to the defence, prosecutors said.

New information showed one of the suspects was convicted of engaging in serial rape and sexual assault, they added.