Travellers who ride the MTR with their packaged infant milk formula must now undergo security checks at Sheung Shui station to ensure they are not carrying too much of the product before they can board the train to the mainland. Photo: Felix Wong

Security check at Sheung Shui station. Photo: Felix Wong

Travellers must undergo security checks at Sheung Shui station before they can board the train to the mainland. Photo: Felix Wong