A 15-year-old arrested along with another 10 people after a ton of heroin was seized in a residence in Filothei, northern Athens, and a warehouse in Koropi, last Thursday, was conditionally released on Monday.
The teenager is the son of a 40-year-old businessman involved in shipping and his former wife, both of whom are facing charges in the probe.
According to sources, the 15-year-old had send a text message from his mobile phone to an Albanian national, also involved in the case, at the time of the police operation in Filothei.
The Albanian initially evaded arrest but eventually surrendered to authorities over the weekend.
Police believe the heroin came from Iran and arrived in Greece via Turkey and was destined for Belgium and Germany.
The street value of the drug was being estimated at 30 million euros.