The Customs have traced the iPhone to Vinodhini, who was found to have used it till the infamous Kerala gold smuggling case surfaced in July 2020.
The ED might come under pressure if the contents of the letter also referred to the matters conveyed in the confidential statements submitted before the court.
The ED and Customs would chart their further course of action after discussing the matter with legal experts.
The statement filed by Customs (Preventive) Commissioner Sumit Kumar kicked up a political storm in the poll-bound state with opposition parties attacking the chief minister.
The Enforcement Directorate is also preparing to defend itself against the Kerala government bid to corner it alleging mental torture of a few officials
Pinarayi claimed Muraleedharan, on multiple occasions, had said the baggage seized by the Customs was not a diplomatic one.
Union Minister and BJP leader V Muraleedharan dismissed as 'childish' the CPM's allegation that the BJP was politically using the probe agencies.
Swapna was questioned several times by various agencies, including the National Investigation Agency (NIA), from July 2020.
CPM said the intention of the central government has become clear with the Customs submitting a 'secret statement', given by one of the accused months ago, just after the election was declared.
According to a copy of an affidavit submitted by the Customs to the Kerala HC, Swapna Suresh claimed the CM had direct contact with the Consul General and had financial dealings with him.