Amazon has warned its wireless earphones may be at risk of overheating and is urging customers to update their software, to make them safe.

Customers were sent an email on Wednesday, saying in “very rare cases” Echo Buds could overheat in their charging case.

Amazon said it had released a software update to fix the issue "out of an abundance of caution".

“The safety of our customers is our top priority,” it said.

Amazon would not say if this meant the earphones could catch fire or explode, but did disclose that its investigation had been prompted by a concerned customer getting in touch.

Amazon said owners would automatically receive the update when the Echo Buds were connected via Bluetooth to a mobile phone and the Alexa app.

It also said if the Echo Buds were a gift, the customer should alert the recipient immediately.

The earbuds are still for sale on the Amazon site but labelled as "out of stock" until late August.

The details of the email were shared by Daniel Bader, managing editor at the Android Central technology blog.

“We are writing to inform you about an important software update for your Echo Buds,” the email said.

“We recently determined that in very rare cases it is possible for Echo Buds to overheat while in the charging case."

The email also said the same software update "improves the long-term performance of Echo Buds' batteries".

Many brands of wireless earbuds have their own battery inside the case, which automatically charges the earbuds when they are placed inside.

Battery heat is often given out by devices while charging but usually stays within strict safety limits.

Amazon did not say if the heat problem was caused by overcharging or any other specific issue within the battery case.

To check if your buds have updated:

Open the Echo Buds case
Ensure both buds are in the case
Confirm they are Bluetooth connected to a phone
Open the Alexa app
Select “Devices” in the bottom right
Choose “Echo & Alexa”
Choose “Echo Buds”
Scroll to the “About” section at the bottom of the page
Confirm the device is running software version 318119151 or higher

If you have a different software version:

Open the lid of the case with the Echo Buds inside
Confirm they are Bluetooth connected to a phone and the Alexa app
Check the buds and case are at least 30% charged
Close the case lid with the buds inside
Stay within Bluetooth range of the phone for 30 minutes
Check the software version is 318119151 or higher, following the instructions above