Ocado has posted an increase in sales in its first quarter, when a fire hit its Andover warehouse.

Ocado reported an 11.2% rise in retail revenue to £404m in the period to March, when the blaze hit sales by 1.2%.

The etailer, which is to create a joint venture with Marks & Spencer, reported underlying 11.3% growth in average orders per week to 314,000, but the average order size was slightly down – by 0.2% to £110.24.

Ocado chief executive Tim Steiner said: “Our first quarter was characterised by continued strong underlying growth in Ocado Retail but also the initial impact of the fire at our [customer fulfilment centre] in Andover on our headline numbers.

“The fire has been a setback, but it will be only a temporary one. Over the last few weeks, our teams have been working hard to minimise any disruption to our customers and we will build a state-of-the-art replacement facility that reflects all the innovations and improvements we have made since Andover opened in November 2016.

“At the same time we all remain focused on delivering customers the very best service, quality, choice and value. Our commitment to these objectives underpinned the underlying progress we made in the quarter.

“With the joint venture signed with M&S at the end of February, Ocado Retail has never been in a stronger position to lead channel shift while constantly setting the bar for excellence in online grocery in the UK. We are looking forward to the future with excitement and determination.”

The etailer said that its initial assessment of the causes of the Andover fire “gives us confidence that, going forward, there are no significant implications for the risk profile of the assets or the viability of our model and therefore for either Ocado Retail or Ocado Group”.