A loud siren has been going off in the Cattedown, Lipson and St Jude's areas of Plymouth since 7am on Thursday morning - PlymouthLive has enquiries in with the authorities and we will be updating this blog as and when we receive more information

A loud siren has been ringing out across Plymouth since about 7am on Thursday morning. Residents in Cattedown, Lipson, Prince Rock and St Jude's can all hear the alarm.

It is unclear at this stage where the alarm is coming from, but PlymouthLive has enquiries in with the authorities and we will be updating this blog as and when we receive more information.

The alarm came to an end at 7.16am and briefly returned at 7.17am. It then rang very briefly again at 7.20am. It is understood Devon and Cornwall Police have been contacted by worried residents in the city.

One resident said: "20 minutes of this? Cattedown area. Coming from the sea? Ships horn? Alarm? Very intense and loud."

Another said: "It sounded almost like the alarm that goes off from the dockyard at 11.30am on a Monday morning."

It is understood a 101 call handler told one caller that they were aware of the siren but were unsure what it was at this stage.

Updates will follow in the live blog below

More on this morning's incident here.

The cause of the siren was a false alarm at our site in Plymouth. All procedures were followed and the system was reset

PlymouthLive is waiting to hear back from the council and the harbour master

We have received a call from a member of the public stating that there is an alarm going off from an unknown location – we are not in attendance at this time.

It seems to be coming from the Cattedown area. More follows

The alarm has now stopped.

The alarm started ringing at about 7am. It wound down at 7.17am but then started up again before stopping. A few minutes later, at 7.20am, there was another, very short burst.

We will update this blog as soon as we know more

I started hearing the alarm at about 7am. At first I thought it was something within the house, but then realised it was coming from outside. I opened the back door and could hear the noise even more intensely. I couldn't work out what it was or where it was coming from. It was actually a bit scary as it almost sounded like the alarm that comes from the dockyard at 11.30am on a Monday, especially when the siren started winding down at 7.17am. There were then two short bursts of it returning. It is a bit worrying hearing an alarm like that unexpectedly, when you don't know what it is.

PlymouthLive currently has calls in with the police, the council and the MoD. This live blog will be updated as soon as we know more.